This disclosure relates to the field of wellbore reaming tools used to enlarge the diameter of a wellbore that has been drilled by a drill bit. More specifically, the disclosure relates to reaming tools having shear cutters and gouging cutters.
U.S. Patent Application Publication No. 2004/0159468 discloses a reaming tool that may be used in a drill string behind a drill bit located at one end of the drill string. The reaming tool disclosed in the '468 publication may provide the ability to enlarge a wellbore drilled by the drill bit to a larger diameter than that drilled by the drill bit. The foregoing reaming tool may have reaming blocks fixedly attached to a reamer tool body, or may have reaming blocks that may be expanded to a selected diameter using any one of a number of well known diametrically expandable mechanisms, such as hydraulic cylinders and associated hydraulic rams.
The reaming tool described in the '468 publication may comprise a plurality of shearing type cutting elements (“shear cutters”), for example and without limitation polycrystalline diamond compact (PDC) cutters. PDC cutters may be configured, for example, by affixing a polycrystalline diamond “table” on a substrate. The substrate may be formed for example, from material such as tungsten carbide or steel having a wear resistant outer layer, such layer made from material such as tungsten carbide. The foregoing configuration of shear cutters is not intended to limit the scope of the term “shear cutter” as used in the present disclosure. Shear cutters may also be made entirely from tungsten carbide or other metal carbide without a diamond table, or may have a cutting table made from other materials such as cubic boron nitride (CBN). Such shear cutters may also be configured in any other manner known for use in shear cutters of fixed cutter drill bits and reaming tools.
In some subsurface earthen formations, reaming a wellbore using a reaming tool having only shear cutters has proven disadvantageous. Such subsurface formations have shown a tendency to cause breakage of the shear cutters. Gouging type cutters are used in drill bits for drilling mine shafts or tunnels, among other uses. Such drill bits are known in the art as “claw” bits, one example of which is sold under the trademark QUI-KLAW, which is a trademark of Drillhead, Inc. Such drill bits are known to be useful in drilling formations such as clay, unconsolidated sand, loose rock and gravel.
U.S. Pat. No. 8,505,634 issued to Lyons et al. describes a drill bit having gouging cutting elements disposed adjacent to shearing cutting elements on a blade on the bit body. The shearing cutting elements have a planar cutting face, while the gouging cutting elements have a non-planar cutting face, e.g., dome shaped or cone shaped, also referred to as “ballistically shaped.”